In a mechanical seal serving as one example of the sliding parts, performances thereof are evaluated by a leakage amount, a wear amount, and torque. In the prior art, the performances are enhanced by optimizing sliding material and sealing face roughness of the mechanical seal, so as to realize low leakage, long life, and low torque. However, due to raising awareness of environmental problems in recent years, further improvement in the performances of the mechanical seal is required, and there is a need for technical development going beyond the boundary of the prior art.
Under such circumstances, the present applicant filed an application for a patent on the invention of sliding parts in which no leakage is caused in a static state, the sliding parts that are actuated with fluid lubrication in a rotating state including an initial stage of rotation while leakage is prevented, so that sealing and lubrication can be realized at the same time (hereinafter, referred to as the “prior art”, see Patent Citation 1).
As one embodiment of this prior art, as shown in FIG. 6, sliding parts in which an outer peripheral side of sliding parts 20 including annular bodies serves as a high pressure fluid side and an inner peripheral side serves as a low pressure fluid side, a groove section 22a of a Rayleigh step mechanism 22 that forms a positive pressure generation mechanism is provided on a high pressure side of a sealing face 21-1 of one sliding part 20-1, a groove section 23a of a reversed Rayleigh step mechanism 23 that forms a negative pressure generation mechanism is provided on a low pressure side of a sealing face 21-2 of the other sliding part 20-2, the groove section 22 of the Rayleigh step mechanism 22 and the groove section 23a of the reversed Rayleigh step mechanism 23 respectively communicate with the high pressure fluid side via radial grooves 24-1 and 24-2, and are isolated from the low pressure fluid side by flat land sections R are proposed. Groove depth of the groove section 22a and the groove section 23a is about a few μm, and groove depth of the radial grooves 24-1 and 24-2 is about 10 μm. The groove depth of the radial grooves 24-1 and 24-2 is sufficiently greater than the groove depth of the groove section 22a and the groove section 23a. 